1. Field of the Invention
The present invention relates to a rotary medium driving apparatus, which is installed in a driving apparatus such as a hard disk drive (HDD) and drives a rotary recording medium.
2. Description of the Related Art
FIG. 7 is a magnetic disk driving apparatus of the prior art. In FIG. 7, the magnetic disk driving apparatus 901 of the prior art is constituted of a rotor 903, which is supported by a shaft 918 fastened to a stator 904 with rotating freely by way of upper and lower ball bearings 916 and 917. Further, the rotor 903 is provided with an outer cylindrical surface 911a of which diameter is assigned so as to fit to a center hole of a magnetic disk (not shown) to be rotated.
In other words, the magnetic disk driving apparatus 901, which is allocated within a cleansed space of a hard disk drive (HDD), comprises a hub 911 of which an outer circumference area is provided with the outer cylindrical surface 911a and a seating surface 911b for mounting at least one magnetic disk so as to fasten the disk securely.
Furthermore, the magnetic disk driving apparatus 901 comprises the rotor 903 including a magnet 912, a rotor yoke 913, and the hub 911 and the stator 904 including a coil 914 for driving the rotor 903 and a stator core 915.
Inner wheels of the upper and lower ball bearings 916 and 917 are fixed to the shaft 918 by press fitting or gluing, while outer wheels of the upper and lower ball bearings 916 and 917 are fixed to the hub 911. The rotor 903 is supported by the shaft 918 with rotating freely by means of the upper and lower ball bearings 916 and 917.
The stator 904 is composed of a housing 902 formed by the aluminum die casting method as a main component of the stator 904. The stator core 915 wounded up with the coil 914 is allocated on an outer circumference of a projection, which is formed on a surface being perpendicular to the shaft 918 and faces toward the rotor 903. The shaft 918 is fixed in a through hole provided at a center of the housing 902.
The housing 902 mentioned above is finished by a machinery cuts so as for the outer circumference surface of the projection for installing the stator core 915 and an inner surface of the through hole for fixing the shaft 918 to become concentric circles after the housing 902 is formed by the aluminum die casting method. Concentric degree of the stator core 915 and the shaft 918 is improved by the machinery cuts mentioned above. Accordingly, the magnetic disk driving apparatus 901 can maintain a rotation performance in high accuracy.
As mentioned above, the housing 902 is finished by the machinery cuts so as for the projection for the stator core 915 and the through hole for the shaft 918 to become the concentric circles.
However, a member formed by the aluminum die casting method further requires to be processed by the machinery cuts. The machinery cuts is high in process cost. Further, cutting oil utilized for machinery cuts and cleaning liquid remains inside porous on a surface on the member processed by the machinery cuts as residues. These residues evaporate after the magnetic disk driving apparatus is installed in an HDD and cause a problem such as a head crush by hydrocarbon, which is an ingredient of cutting oil and evaporated from the residues, absorbed by a head of the HDD and a magnetic disk loaded in the HDD.
In addition thereto, if sulfur contained in cutting oil as additive evaporates or chlorine contained in chloric cleaning liquid evaporates, a surface of a disk is corroded. Accordingly, another problem occurs such that data recorded in the disk disappear or are erased.
Accordingly, in consideration of the above-mentioned problems of the prior art, an object of the present invention is to provide a rotary medium driving apparatus in high reliability, which comprises a flat base or a flat housing formed by a presswork. Further, the rotary medium driving apparatus can eliminate a problem of deteriorating reliability caused by chemicals, which stick on a head or a disk, evaporated from residues and cutting oil utilized while processing a stator housing by a machinery cuts.
In order to achieve the above object, the present invention provides, according to an aspect thereof, a rotary medium driving apparatus comprising a rotor of being able to rotate freely around a shaft fixed to a stator by means of ball bearings and being provided with an outer circumference surface having a diameter of being able to engage with a center hole of a rotary medium to be rotated, the rotary medium driving apparatus is further characterized in that the stator comprises a flat housing formed by a presswork and a stator core allocated in a vicinity of center of the flat housing, and that the flat housing fixes the shaft.
According to another aspect of the present invention, there provided a rotary medium driving apparatus comprising a rotor of being able to rotate freely around a shaft fixed to a stator by means of ball bearings and being provided with an outer circumference surface having a diameter of being able to engage with a center hole of a rotary medium to be rotated, the rotary medium driving apparatus is further characterized in that the stator comprises a flat housing formed by a presswork and a stator core allocated in a vicinity of center of the flat housing, and that the flat housing is provided with a ring shaped projection section projected toward the rotor with the shaft fixed on an inner circumference surface of the ring shaped projection section and with the stator core allocated on an outer circumference surface of the ring shaped projection section.
Other object and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.